Recapture depriciation with owner financing

[Jared Dullum]

Im trying to better understand depriciation and recapture when selling.

I have an owner of a package of duplexes that I'm trying to structure an owner-finance deal. They are only willing to finance a small amount as they say the money down they need to cover the taxes owed from recapturing all the depriciation over the years.

What are the rules on recapturing depriciation when a seller wants to owner finance the sale? 

In my example the seller has 30 units (15 duplexes) and will sell for $1.2 million but wants $900,000 down so as to pay taxes on what they have depriciation over the years. I wanted to give them much lower down payment And have them finace the bulk of the purchase price. How would that affect what theybowe or how they pay taxes??